url: improve isURL detection

Author: anonrig

lib/internal/url.js

@@ -692,11 +692,14 @@ ObjectDefineProperties(URLSearchParams.prototype, {
  *
  * We use `href` and `protocol` as they are the only properties that are
  * easy to retrieve and calculate due to the lazy nature of the getters.
+ *
+ * We check for auth attribute to distinguish legacy url instance with
+ * WHATWG URL instance.
  * @param {*} self
  * @returns {self is URL}
  */
 function isURL(self) {
-  return Boolean(self?.href && self.protocol);
+  return Boolean(self?.href && self.protocol && self.auth === undefined);
 }
 
 class URL {

test/parallel/test-url-is-url.js

@@ -0,0 +1,11 @@
+// Flags: --expose-internals
+'use strict';
+
+require('../common');
+
+const { URL, parse } = require('url');
+const assert = require('assert');
+const { isURL } = require('internal/url');
+
+assert.strictEqual(isURL(new URL('https://www.nodejs.org')), true);
+assert.strictEqual(isURL(parse('https://www.nodejs.org')), false);